Nose job brings fuel savings

JANUARY 31, 20014 — Copenhagen, Denmark, headquartered Clipper Group says it is seeing fuel savings of 8.5% as a result of bulbous bow and rudder bulb modifications made on a 2011-built G-type 9,100 dwt multipurpose carrier, Clipper Galaxy.

The bulbous bow is a very important part of the hull as it can potentially reduce the hull resistance considerably, or affect the resistance in a negative way, says Clipper Group. Designing the perfect bulb is delicate and the efficiency depends on the speed and loading/draft of the vessel.

In the past a bulb was usually designed and optimized to full speed and close to full load condition. Today,though, most vessels are operated at eco-speed in part load conditions. Multipurpose vessels, in particular, are seldom operated in full load conditions.

The bulb of Clipper Galaxy was modified during drydocking at Lixin Shipyard in Shanghai in August 2013. The existing bulb was cut off and a new bulb with a different size and shape was fitted instead. At the same time Clipper also designed and fitted a rudder bulb, improving propeller efficiency by 2-3%.

The saving of the bulb modification alone would be above 10%, but trim optimization outweighed some of the disadvantages of the old bulb. Actual savings will also vary depending on loading and speed conditions. However, looking at the consumption before and after the modifications, as well as the current loading and speed patterns, the overall saving is around impressive 8.5% - including the rudder bulb effect.